hard to start/no power

[01txdmax]

hey yall, I have a buddy that has asked my help in troubleshooting his 99 7.3L. lucky me

The truck is mostly stock but has an aftermarket turbo (dont know what kind) a basic hypermax programmer of some flavor. the truck acts the same with the stock and the 'performance' tune in it. the truck has been run with jp-5 and b2

The truck is hard to start, then once you get it started idles really rough, almost wants to die. The engine rpms increase very slowly when you apply the go pedal, and never smooths out regardless of rpm. no smoke to boot, and no check engine light at idle or higher rpms with transmission in park or neutral. when the truck was driveable he would get a check engine light only under hard acceleration, but would go away as soon as he got out of it.

since the gripe showed up he has went back to b2, changed the fuel filter and changed the oil.

I have limited knowledge of 7.3's, but it sounds to me like either a fuel supply to the injection pump, the pump itself or a hpop issue. am I way off base? is there any easy way to troubleshoot this other than shot gunning parts?

 

[h2odrx]

I'll take a stab and say it might pay to drop the tanks and check the pick ups?

 

[01txdmax]

I may try that, depending on how much fuel is in the tanks. I was thinking of pressurizing the tanks a little to see if maybe the lift pump wasnt pushing enough pressure/volume to the injection pump too.

I've been reading that the ICP going bad can cause similar issues, so I'm going to try disconnecting that too.

 

[h2odrx]

That is my guess, did yall check the FPR? clean the screen? 99 has a electric pump right?

 

[01txdmax]

I dont know for sure. I'll get the truck to my house on friday, just looking for suggestions on things to try.

 

[li'l tugger]

an easy way to check for crud in the tank without dropping the tank would be to open the fuel bowl, drain off any #2 in there and refill it with fresh clean #2 from a different source. just pour some straight into the bowl, replace the filter and lid, give it a start. this should tell you if it's bad fuel, bad pickups, etc. my 99 did a similar thing the other day. i was at the bottom of my tank and the truck started running rough. it got worse and worse until it died. i pulled off the road, checked all the visible stuff, said a few choice cusses. then i pulled the fuel filter, which was fairly clean. i drained the old fuel out of the bowl. i just happened to have 5 fresh gallons in the bed so i poured some in the bowl.. reconnected and started up again. it ran rough for a couple of seconds, but smoothed out. in my cas it was bad fuel, or i picked up too much crud being at the bottom of the tank. i made it to the nearest buccee's and filled up. i also gave her a ****** of diesel treatment and cetane boost with just a little straight into the bowl. fixed her right up!

 

[tonkadoctor]

There is no injection pump on the powerstrokes

fuel goes to the fuel rail cast into the heads and high pressure oil fires the injectors when the injector driver module fires the solenoid


Sounds like a high pressure oil pump related problem, next time it won't start, pull the plug on the HP oil resevoir, oil level should be 1" from the top. If not you are losing the HP oil prime somewhere, either bad LP lube pump/ timing cover or injector o-rings

IIRC, disconecting the ICP causes the computer to default to 700 psi HP oil pressure which will let it run. Engine will fire up at about 500 psi

Could be a bad IPR valve or even the HPOP too.

Now if it is a problem on the fuel side.... IIRC it needs about 50 - 55 psi minimum in the fuel rails to run which could be plugged pickup, bad fuel pump, bad FPR valve or injector o-rings

 

[01txdmax]

tonkadoctor, I am kinda on the same side of this, it sounds like a hpop gripe. with no smoke, no power, poor idle, hard starting.

where exactly is the hpop resevoir and the icp sensor? and what's a icp?

 

[Mike]

HPOP is front and center on the engine, there should be a 1/4 inch pipe plug right on the top of it. The ICP is the sensor that reads the injection pressure on the oil side of the system, it will tell the IPR valve to open of close to supply the desired pressure to the injectors.

Has the glow plug relay and or glow plugs been verified as good as of yet?

 

[01txdmax]

no, I'm just going to get the truck right now.

If the glow plugs werent operating wouldnt there be smoke on start up and 'shouldnt' the motor smooth back out and run properly at higher rpms?

thanks

 

[01txdmax]

well, the glow plugs come on and go off as if they are operating normally. the electric fuel pump is making a seemingly proper noise and getting 12v, so supply fuel is getting to the filter bowl. the filter bowl (minus the filter) fills up to the threads in @ 20 sec with the key on. there is no trash in the bottom of the bowl.

if i ended up in the right spot i disconnected every sensor on the hpop one at a time with no change in the ability to start the truck. i even tried the sensor that is on the driver side valve cover on the inboard side, no dice.

the truck is sitting on the battery charger for the night, going to do some more looking in the am.

 

[01txdmax]

ok, so we replaced the drivers side, forward most glow plug, kinda but not really helped starting the truck.

oil pressure on the gauge takes a count to nearly 5 mississippi to reach normal..... is that normal?

so here is the ***? if we open the fuel filter bowl purge valve the truck smooths out and idles normal as soon as you shut the valve the truck dies again..... any ideas?

 

[h2odrx]

you talking about the water drain? that is weird how much fuel in tanks? and when and where was it bought might be bad fuel?

 

[01txdmax]

I dont know, it's been in the tanks for a while. I told a buddy of mine how long it took to fill the filter bowl and he is convinced that the frame mounted pump isnt making the pressure/volume it should. He thinks the 50/50 jp5/b2 blend caused the pump to start failing.

I'll try to get him to drain the tank and start with fresh fuel, see where that get's us.

 

[Jeep1947]

Could be the o rings on the IPR.